The present invention relates to a flexible magnetic disk apparatus and a rigid magnetic disk apparatus, more particularly to a magnetic disk apparatus having resistance properties against external impact and vibration.
Magnetic disk apparatus which have been installed in desktop computers heretofore are now becoming to be installed in portable (mobile) computers and information appliances other than computers. Consequently, their possibilities to receive disturbance are becoming higher. Troubles of those magnetic disk apparatus caused by such disturbances are roughly classified into two types; troubles in non-operation in which information writing/reading is performed and troubles in operation in which information writing/reading is stopped. The former troubles include deviation of magnetic disk rotation centers, damages of the magnetic disks and/or heads, and troubles in a spindle motor system used to rotationally drive the magnetic disks. The latter troubles, in addition to the former troubles, include information writing/reading errors, as well as magnetically destroy of recorded information, in the worst case.
JP-A-5-36221 specification discloses a magnetic disk apparatus that is detachable from an information processing apparatus to avoid the above-described troubles. The magnetic disk apparatus has a manually operated mechanism that mechanically locks both of a head arm for positioning a head and magnetic disks when the magnetic disk apparatus is detached from the information processing apparatus and unlocks them when the magnetic disk apparatus is attached to the information processing apparatus.
Further, unlike the above-described prior art in which the head arm and the magnetic disk are latched by manual operation, there are other known arts to latch those items automatically by mechanical or electrical operation as described hereinafter.
At first, a latch mechanism to latch a movable part of a head carriage with the use of inertia of the mechanism against vibrations and impact from the outside of a magnetic disk apparatus is disclosed in U.S. Pat. Nos. 5,870,256 and 5,875,075. A latch mechanism to latch a movable part of a head carriage electromagnetically in response to a trigger is disclosed in JP-A-11-96699 specification. A latch mechanism to latch a movable part of a head carriage with use of a piezoelectric element in response to a trigger is disclosed in JP-A-11-273277 specification. A latch mechanism to latch a movable part of a head carriage with use of a shape memory alloy in response to a trigger is disclosed in U.S. Pat. No. 5,982,586. A latch mechanism to latch a movable part of a head carriage with use of an air flow caused by the rotation of a disk is disclosed in U.S. Pat. No. 5,999,371. A latch mechanism in which the above-described inertial mechanism and electromagnetic means are combined is disclosed in U.S. Pat. No. 5,877,922. Each of the above-described devices uses means for latching a head carriage.
On the other hand, a latch mechanism in which part of a movable portion of a carriage comes into contact with an edge of a disk when the head is unloaded with the use of a loading/unloading mechanism of the head is disclosed in JP-A-11-238331 specification.
The mechanism disclosed in JP-A-5-36221 specification locks the movable part when the magnetic disk apparatus is detached from the information processing apparatus. When the magnetic disk apparatus is attached in the information processing apparatus, the condition of the magnetic disk apparatus is one in which the lock has been released. Therefore, there is a possibility that the following disadvantages occur.
When a mobile computer and/or an information appliance itself is carried, there are much possibilities to give an impact to the magnetic disk apparatus by an accident to drop the mobile computer and/or the information appliance with the magnetic disk drive installed therein. Any of the prior arts described above gives no consideration to the external impact to be applied to the magnetic disk apparatus installed in the host information processing device. Further, there is possibility to result fretting wear at a bearing portion of a disk spindle by vibration from the outside.
In the latching mechanisms of the inertia and/or electromagnetic means, the head carriage is latched when the magnetic disk drive is in non-operation independent of existence of a host machine. Each of the above-described prior arts except the art disclosed in JP-A-11-238331 specification just relates to a mechanism that latches the head. The mechanism disclosed in JP-A-11-238331 specification is structured so that a stopper operationally associated with the head carriage comes in contact with an edge portion of the disk when the head is in an unloaded state (when the head is parking on ramp). Consequently, unless the rotation of the disk is stopped at the moment the head is unloaded, the stopper will come in contact with the rotating disk, thereby the edge of the disk is worn or, the disk is damaged in the worst case. In addition, the mechanism is structured so that the disk is pressed at one circumferential point of the disk in the radial direction, so that there is possibility that fixing position of the magnetic disk with respect to the spindle motor might be deviated from its regular position.
In the case of effecting random data writing/reading, the rate of the reading/writing time to the whole operation time of the magnetic disk apparatus for the consumer use is 1% or less. Consequently, even when the magnetic disk apparatus is in a condition that it is installed in a mobile computer or an information appliance, the magnetic disk apparatus does not effect its primary operation during almost time. On the other hand, in the case of effecting sequential data writing/reading, writing/reading is continuously effected and the magnetic disk apparatus is always exposed to the menace of impacts, vibrations, etc.